Treatment of metal surfaces in frictional contact to increase the friction therebetween



March 11, 1959 J. w. RYZNAR 2,877,716 7 TREATMEN F METAL SURFACES IN FRICTIONAL CONTACT T0 REASE THE FRICTION THEREBETWEEN Filed Aug."8, 1956 m m m m YZNAR United "tates Patent TREATMENT OF METAL SURFACES 1N FRIC- TIONAL CONTACT TO INCREASE FRIC- TION THEREBETWEEN 12 Claims. (Cl. 104-1) This invention relates to a new and improved adhesion treatment of metal surfaces and more particularly to a method and composition for increasing the coefficient of friction between metal surfaces capable of motion one with respect to the other. The invention is especially concerned with the provision of chemical means for preventing wheel slippage between locomotive wheels and rails. However, in its broader aspects the invention contemplates the improvement of frictional contact be tween metal surfaces which are susceptible of slippage one with respect to the other, as, for example, the slip page which occurs between a shaft and a sheave, gear or pinion frictionally mounted on said shaft.

The past several decades have produced railway locomotives possessing great power and weight, thus enabling long, heavily-laden trains to be pulled by single engines. With the advent of the extremely heavy locomotive it was felt that driving wheel slip would be eliminated. It was soon discovered, however, that the increased static weight carried on the driving wheels did not solve the problem to any great extent. Track sanding techniques were developed but this only partially alleviated the condition. Wheel slippage has proven to be an erratic condition which has not in all cases been satisfactorily explained. I

In one explanation of the problem, rail slip is said to result from a tough invisible oil film on the wear band of the rail. Traffic and heat destroy this film and high adhesion results. When a light rain occurs or when the rails reach the dew point, as the result of the relatively high humidity, a water film forms across the wear band where it may contact oil deposits on the edge of a rail with the result that a film of oil creeps through and replaces the water film. The oil deposits on the rail sides acts as reservoirs for the formation of new oil films and water acts as the transporting agent. The oil deposits on the rail come from journal box oil leakage by way of the outside face and outer portion of the tread of the car wheels. There are other sources of contamination such as road crossings, rail lubricators, and the like.

The importance of solving the problem is strikingly illustrated when it is realized that only 15% of the engines weight can be utilized as tractive force when the rails are greasy and moist, and 30% when the rails are clean, dry and sanded. Even a small improvement in these figures, as expressed in the terms of increased coeificient of friction, would enable railway locomotives to operate more etliciently and economically as well as providing improved braking for railway locomotives and rolling stock.

Another instance where it is desirable to improve the frictional contact between two metal surfaces capable of motion one with respect to the other is where a gear or pinion is frictionally mounted on a shaft. Obviously, if. slippage occurs between the gear or pinion and the shaft the efficiency of the particular operation in question is reduced or the device may even become inoperable.

friction between said surfaces.

It is, therefore, an object of this invention to provide a new and improved method for enhancing the frictional contact between two metalsurfaces capable of motion one with respect to the other.

Another object of this invention is to provide a method for raising the coefficient of friction between railway car wheels and rails.

Still another object is to raise the coefiicient of .friction between railway car wheels and rails having an oil film thereon.

A further object is to provide a method of decreasing slippage between railway wheels and rails.

Another object is to provide a chemical treatment .to prevent locomotive slippage on dry, wet, or oily rails.

Still a further object is to enable railroad locomotives to utilize more of their tractive forces on wet oily rails than has heretofore been considered possible.

An additional object of the invention is to produce a railway rail containing an adherent coating of a mate rial which substantially prevents slippage between the rail and a locomotive or railway car wheel.

Still a further object is to provide a method of substantially preventing slippage between the bearing surfaces of a railway rail and a locomotive or a railway car wheel by applying to the rail and/or wheel aliquid coating material which evaporates leaving a thin film or coating of a slip inhibiting substance. 1 1

In accordance with the invention -it has been found that the coefiicient of friction between contacting metal surfaces capable of motion one with respect to the other. can be increased by applying to at least one of the contacting surfaces a thin film of synthetic alumina-silicate zeolite gels and sols, either washed free of salts or as prepared. The invention in its preferred embodiment is particularly applicable to improving the coefiicient of friction between railway tracks and railway engine and car wheels by applying to at least one of the contacting surfaces thereof a film of zeolite. a

In the drawing Fig. 1 shows a perspective view of a section of a railway rail containing a coating consisting essentially of a zeolite film applied to the bearing surface thereof.

Fig. 2 is a perspective view of a flanged wheel used on rail-type transportation vehicles such as railroad engines and cars.

As shown in the drawing, the rail 1 has a bearing surface 2 to which a continuous coating 3 of zeolite is applied. The coating of zeolite may also extend over the surface 4 which comes into contact with the wheel flange of the wheels of railway engines and railway cars; although for the most part it is more desirable to' leave the surface 4 uncoated to minimize wear of the wheelfianges.

The wheel 5 having a flange 6 contains a continuous coating 7 consisting essentially of zeolite applied to the load bearing surface thereof. While it is usually more desirable to leave the surface 8 of the wheel flange un coated for the foregoing reason, a coating of zeolite may alsobe applied to this surface of the flange which comes into contact with the rail.

An important feature of the present invention resides in the fact that synthetic alumina-silicate zeolite can be prepared in the form of aqueous gels or sols. When the gel or sol is applied to the bearing surface of a metal coming into frictional contact with another metal, as is,

the case with rails and wheels. of railroad engines and cars, the evaporation of the water, or other liquid carrier medium, leaves a thin, highly adherent, substantially continuous film or coating which imparts to the metal surfaces pronounced improvements in the coeflicient of, In the simplest method" of practicing the invention, therefore, an aqueous gel or sol of zeolite is applied either to the steel rail or to the contact surface of a locomotive wheel or railway car wheel or to both the rail and the wheel.

If the zeolite sol or gel is applied to a moving metal surface such as an engine drive wheel it is desirable that the product by dry 'or semi-dry by the time the wheel contacts the rail. To this end the application of the sol or gel is advantageously effected by a method involving blowing with air or other gas which assists in the evaporation of the volatile liquid. The zeolite in gel form is ap plied by applicators suited for the application of gellike or paste materials such as a rotating wheel to make contact with said metal surface and a body of the 'gel.

Zeolites contain combined water, sodium oxide (Na G), alumina (A1 and silica -(SiO in various ratios. Usually the Na O:Al O molecular ratio is about 1:1, but the alumina-silica ratio may vary considerablyranging from about 1:2 to as high as 1:15. The sols and gels of zeolites may be prepared by mixing together in various proportions solutions of sodium silicate, such as diluted commercial water glass solutions, sodium aluminate solutions and a strong acid such as sulfuric acid. By varying the ratios of the solutions, the pH and the Al O :SiO ratio can be controlled. One method for making zeolite gels is described in considerable detail in U. S. Patent No. 1,906,202 issued April 25, 1933 to William A. Bruce.

The following examples are supplied as illustrations of methods for preparing sols and gels in various ratios and l at various pHs. All parts are by weight unless otherwise designated.

Three solutions designated A, B and C were prepared as follows. Solution A was made by diluting 36.8 parts of commercial water glass solution with 314 parts of EXAMPLE I A mixture of cc. of solution A and 9.4 cc. of solution B, to which was added 3.2 cc. of solution C, gave a sol which quickly gelled and had a pH of 10.7. The Al O :SiO ratio was 1:8.

EXAMPLE H A mixture of 35 cc. of solution A and 9.4 cc. of solution B, to which was added 10 cc. of solution C, gave a solution which gelled after five days and had a pH of 3. The Al 0 :SiO ratio was 1:8.

EXAMPLE III A mixture of 18.2 cc. of solution A and 10 cc. of solution B gave a quickly gelling sol which had a pH of about 11. The Al O :SiO was 1:4.

Evaluation of increase in friction between surfaces In order to evaluate various zeolite solutions and gels as agents for improving the coeflicient of friction between metal surfaces in frictional contact and capable of motion relative to one another, the following test apparatus was employed.

A steel rail was used as the base surface upon which the test was run. A U-shaped member made of heavy strap steel was formed having two perpendicular pieces attached to the tips of the U. A diameter hole was bored in the center of the base of the U. A 1%" diameter steel ball having a Brinell hardness of 500 was welded to a. threaded steelv rod. The threadedsteel rod was placed in'the hole formed in the U-shaped steel member and fastened with a nut so that the steel ball was within the cradle of the U. The perpendicular arms were fitted with small steel boxes capable of holding lead shot or other weighted material. The U-shaped member was of the rail.

placed on the rail so the steel ball rested on the surface To either side of the inverted U, wires were attached at a point slightly above the rail surface. Fixed to the other ends of the wire was a short piece of string that passed over a fixed pulley, the top of which was approximately coplanar with the surface of the rail. At the opposite end of the string was a suspended container which could be filled with weights.

' In operation, the boxes were filled with lead shot in an amount which, when included with the weight of the cradle and fixtures, exerted a pressure at point of contact on the rail of 73,900 pounds per square inch. The weight of the U-shaped member and ball was 3,065 grams, which, for the purposes of experiment, may be considered as the operative downward pressure. The suspended container was filled gradually with lead shot until the steel ball just started to slide. This amount of weight is considered as the force necessary to overcome the friction existing between the ball and the rail. Using these two factors, the coefiicient of friction may readily be solved from the following simple equation:

Coefiicient of friction=g where P equals 3,065 grams and F is the weight necessary to move the 3,065 grams.

During the course of testing various materials, it was necessary to make several modifications of the test apparatus. After using the rail for numerous experiments it was ground fiat to remove surface abrasion and to facilitate cleaning operations. This was later substituted by a '4 inch long piece of polished heat treated steel which was rigidly held in a small wooden frame. The steel piece was 1" wide and A" thick. It had a tensile strength of 164,200 pounds per square inch, a yield point of 159,- 200 pounds per square inch, a percent elongation of 17.3% and a decarburization to a depth of 0.008". An analysis of this steel showed it to contain the following:

Percent by weight Carbon .31 Manganese .58 Phosphorus .016 Sulfur .016 Silicon .29 Chromium 1.000 Molybdenum .22

In using each of these surfaces the blank tests did not vary within experimental error and hence the test method was concluded to be standardized throughout.

At the start of each series of tests the rail and ball were cleaned with scouring powder, rinsed with distilled water and dried with cellulose tissues. Periodic inspections were made of the contacting surfaces and when scratches occurred the ball and rail were polished with emery paper to renew the surface finish.

To simplify the experimental results, the forces necessary to overcome the friction of the steel ball on the rail were recorded in grams. Three types of blank tests were run, the first being conducted with clean dry surfaces. Under these conditions an average of 1835 grams was necessary to move the ball. When a visible film of journal box -oil was applied to the rail. the average was 620 grams. When water was applied to the oil film the average was found to be 720 grams.

.After a number of tests it was determined that tests on the oiled rail alone were sufficient for purposes of comparison. All of the tests hereinafter described were conducted with a film of journal box oil at all times initially apparent on the rail. The designation wet in the following table indicates that the zeolite film was applied to the oiled metal surface and the test conducted before the film dried, whereas dry indicates that the film was allowed to dry prior to beginning the test.

.dry films are shown in Table I.

The results of tests using various gels and sols of zeolites prepared according to the general procedure of the foregoing examples in various thicknesses of wet and The evaluations of the various zeolite films were conducted with the modified apparatus on the 4 inch piece of polished, heat treated steel, described supra.

TABLE I Test Film Wet or How Percent Ave. No. AlgOuSlO pH Thlck- Dry Ap- Solids Force,

ness plied gins.

1:8 Med-.- Dry-.- Gel..- 5- 1,960 1:8 3 Med... Dry... Gel-.. 4 1,010 1:8 3 Med--. Dry... Sel 4 825 1:8 11 Thick- Wet... 801.-.. 5 1,100 1:8 11 Med.-. Dry..- Sol---. 5 880 1:8 10 Thick- Wet..- Gel..- 5- 1,900 1:8 10 Med--- Dry.-- Gel.-- 1,770 1:8 10.7 Thick- Wet-.. Gel--. 5- 2.300 1:8 10.7 Med... Dry.-- Gel.-. 5- 2,100 1:8 10.7 Thin. Dry... Gel.-- 5- 1,150 1:8 8 Thin.. Dry... Gel-.- 4-5 1,000 1:8 6 Thin.. Dry... Gel--. 4-5 1,300 1:8 4 Thick. Dry... Gel.-- 1-5 1,900 1:2 11 Thick- Wet... Gel..- 5 1,800 1:2 11 Med... Dry... Gel..- 5 1,750 1:4 11 Thick- Wet--- Gel--- 5 2,250 1:4 11 Med.-. Dry... Gel..- 5 2,450 1:6 11 Thick. Wet... Gel... 5 1,900 1:6 11 Med.-. Dry... Gel... 5 1,900 1:10 11 Thick- Wet..- Gel.-. 5 1,800 1:10 11 Thin.. Dry..- Gel--. 5 900 1:12 11 Thick- Wet..- Gel.-- 5 2,100 1:12 11 Med--- Dry--- Gel--- 5 1,700 1:14 11 Thick- Wet--- Gel-.- 5 1,800 1:14 11 Med-.- Dry--. Gel-.- 5 1,700

Contains 0.2% Ultrawet D. S., a wetting agent comprising allryl benzene sodium sulfonate. In an independent test on the same apparatus the average force for a film of a solution of Ultrawet D. S. per se was: 600 with a wet film, and 550 with a dry film.

It will be seen from the foregoing discussion that the zeolites may be used in various physical forms, including aqueous gels and sols. Better results are achieved with gels.

In other embodiments the zeolites are dry, fine particle size solids and are suspended in a volatile, nonlubricating liquid in an amount suificient to produce a paste-like product. Examples of suitable nonlubricating liquids, other than water, are methanol, ethanol, isopropanol, ethylene glycol, carbon tetrachloride, benzene, toluene, xylene, dimethyl ether, naphtha and kerosene. By nonlubricating" is meant that the liquid should have no substantial lubricating effect. It is possible, of course, for a liquid to have a slight lubricating effect which is more than counteracted by the adhesion-producing properties of the zeolite particles. In practice of the invention the liquids preferably employed are sufficiently volatile at the temperatures used to permit the formation of a semidry to dry coating which contains only minor portions or no residual carrier liquid. In the preferred embodiment the anti-slip coating is a dry film made from the zeolite gels.

While the invention has been illustrated with respect to improving the frictional contact between wheels and rails, it is contemplated that it can be applied generally to improving the frictional contact between two metal surfaces capable of motion one with respect to the other. In the case of locomotive wheels and rails, the improvement of frictional contact involves contacting parts which are normally in motion (or dynamic) during the period when optimum frictional contact is desired. However, the invention is also applicable to improving the frictional contact between a metal shaft and a sheave, gear or pinion frictionally mounted thereon. In this case, the zeolite is applied as a thin coating to the shaft and the frictionally mounted member is forced on the shaft so that the zeolite is between said member and the shaft. Similarly, the invention may be applied to form a layer, coating or film between bolts and lock-nuts, and also between other parts which are normally desired to remain static. in both dynamic and static applications the optimum effect is obtained when the zeolite is present on the metal surfaces in a semi-dry to dry state.

The invention is hereby claimed as follows:

1. The method of improving the frictional contact between two metal surfaces capable of motion, one with respect to the other, which comprises applying to at least one of said surfaces a coating of a zeolite having an Al O :Si0 ratio between 1:2 and 1:15.

2. The method of improving the frictional contact between two metal surfaces capable of motion, one with respect to the other, which comprises applying to at least one of said surfaces a coating of a zeolite having an A1 O :SiO ratio between 1:2 and 1:15 in a substantially nonlubricating carrier liquid.

3. The method of improving the frictional contact between two metal surfaces capable of motion, one with respect to the other, which comprises applying to at least one of said surfaces a coating of an aqueous zeolite gel, said zeolite having an Al O :SiO ratio between 1:2 and 1:15.

4. The method of improving the frictional contact between the rails and the wheels of a railroad engine which comprises applying to the bearing surfaces of at least one of said wheels and said rails a coating of zeolite having an Al O :SiO ratio between l:2 and 1:15.

5. A method of improving the frictional contact be tween the rails and the wheels of a railroad engine which comprises applying to the bearing surfaces of at least one of said rails and said wheels prior to contact of said hearing surfaces a coating of an aqueous zeolite gel having an Al O zsiO ratio between 122 and 1:15.

6. A method of improving the frictional contact between the rails and the wheels of a railroad engine which comprises applying to and allowing to dry on the bearing surfaces of at least one of said rails and said wheels prior to contact of said bearing surfaces a coating of an aqueous zeolite gel having an Al O :SiO ratio between 1:2 and 1: 15.

7. A structure having two metal surfaces capable of motion, one with respect to the other, and adapted to engage each other by frictional contact, at least one of said surfaces having a coating of a zeolite having an A1 O :SiO ratio of between 1:2 and 1:15.

8. A structure having two metal surfaces capable of motion, one with respect to the other, and engaging each other by frictional contact, at least one of said surfaces having a coating resulting from allowing to dry thereupon a film of an aqueous zeolite gel having an Al O :SiO ratio of between 1:2 and 1:15.

9. A railroad rail, the bearing surface of which is coated with a film of a zeolite having an Al O :SiO ratio between 1:2 and 1:15.

10. A railroad rail, the bearing surface of which is coated with a film of zeolite resulting from allowing to dry thereon an aqueous zeolite gel having an Al O :SiO ratio between 1:2 and 1:15.

11. A flanged, railway vehicle wheel, the bearing surface of which is coated with a film of a zeolite having an Al O :SiO ratio between 1:2 and 1: 15

12. A flanged, railway vehicle wheel, the bearing surface of which is coated with a film of zeolite resulting from allowing to dry thereon an aqueous zeolite gel having an Al O :SiO ratio between 1:2 and 1:15.

References Cited in the file of this patent UNITED STATES PATENTS 2,787,965 Luvisi Apr. 9, 1957 2,787,966 Lyons Apr. 9, 1957 2,787,967 Nohejl Apr. 9, 1957 2,787,968 Luvisi Apr. 9,1957 

9. A RAILROAD RAIL, THE BEARING SURFACE OF WHICH IS COATED WITH A FILM OF A ZEOLIT HAVING AN AI2O3:SI32 RATIO BETWEEN 1:2 AND 1:15. 